Chain saws are typically used to fell trees, trim branches, and cut a variety of materials, among other tasks. They generally include an engine enclosed within a housing, a guide bar extending from the housing, and an endless saw chain loop that may include various links such as, but not limited to, cutter links, center links, side links, tie straps, and drive links. Through use, the cutting surfaces of various links may become dulled and worn. As the cutting surfaces experience wear, an increased amount of force is required to produce a desired cut, which is inefficient and consumes energy. Therefore, cutter links of saw chains are periodically sharpened to maintain efficiency in a cutting operation.
One method of sharpening cutter links includes positioning a sharpening element (e.g. an abrasive stone) within the housing of the chain saw. The sharpening element may be positioned so as to contact the various saw chain links as they traverse a drive sprocket, typically at high speeds. These systems, however, have drawbacks. For example, one or more grooves may be worn into the surface of the sharpening element from the repeated contact of the various saw chain links. Additionally, because the sharpening element is continually present during cutting operations, damage may occur through debris impacting the sharpening element or chain throw, where the saw chain unintentionally impacts the sharpening element. Any defect in the sharpening element may cause the cutting edge to become deformed during the sharpening process or otherwise negatively impact the ability to maintain a proper cutting edge. This may ultimately impact the ability of the chain saw to cut various materials.
Some nose mounted sharpening devices have been used over the years. One example is shown in U.S. Pat. No. 4,597,178. This device includes a long sleeve that is positioned over the nose and extends a good distance along the guide bar. A rotary actuator is positioned at the end of the sleeve to allow an operator to turn the dial to incrementally advance the sharpening stone towards the cutters of the chain. These devices are cumbersome and dangerous, as they require unnecessary operator actuation, and they can tend to over sharpen and cause premature wear and fatigue on the cutters. Another device, such as those shown in U.S. Pat. No. 4,530,258, includes nose mounted sharpeners that have a pivoting sharpening element. These are deficient for many reasons as well. For example, they do not result in an even engagement of the cutters as they traverse the guide bar nose and they do not provide for adequate lateral support of the cutting stone.